Wicket gate overload sensor and protector

ABSTRACT

A strain gauge is provided in the mechanical linkage which operates the hydraulic turbine wicket gates. When the force exerted by the linkage in operating the wicket gates approaches that force which will cause the linkage to fail the change of resistance in the strain gauge initiates a signal which either indicates to the operator that the closing operation should be stopped or stops the closing operation automatically.

United States Patent STRAiN GAGE [72] Inventor John M. Horn York, Pa. [211 App]. No. 885,847 [22] Filed Dec. 17, 1969 [45] Patented Oct. 19, 1971 [73] Assignee Allis-Chalmers Manufacturing Company Milwaukee, Wis.

[54] WICKET GATE OVERLOAD SENSOR AND PROTECTOR 3 Claims, 4 Drawing Figs.

52 us. Cl 137/551,

251/79, 251/308, 192/150, 415/l3,415/l64 [51] Int. Cl ..Fl6k 37/00, F16k 31/44 [50] Field of Search 192/30, 150;415/13, 159, 164; 251/79, 308; 137/551; 174/1, 519; 64/28 [56] References Cited UNITED STATES PATENTS ,782,498 11/1930 Biggs 251/308 2,753,029 7/1956 Babaian 192/150 X 2,754,567 7/1956 Crane 192/150 X 3,060,706 10/1962 Hess 251/79 X 3,313,518 4/1967 Nancarrow. 415/13 3,429,406 2/1969 Cary 192/150 X Primary Examiner-Henry T. Klinksiek Attorneys-John P. Hines, Robert B. Benson and Arthur M.

Streich POWER SUPPLY 1 TO BRIDGE WHEATSTONE co TRO BRIDGE N L 011.

.5 souzmono T RELAY VALVE PovvEP SUPPLY TO RELAY GOVERNOR PILOT SERVO VALVE PATENTEUnm 19 Ian 3,6 13 .72 1

POWER SUPPLY T0 BRIDGE WHEATSTONE BRIDGE COli'lROL OIL 5 SOLENOID Q1 RELAY VALVE STRAIN GAGE POWER SUPPLY TO RELAY GOVERNOR PILOT SERVO VALVE 26- "26 25'? E QS /y/bop/idl WICKET GATE OVERLOAD SENSOR AND PROTECTOR This invention pertains in general to hydraulic machines such as turbines and pump turbines which utilize wicket gates and more particularly to a means for monitoring the stress in the wicket gate actuating mechanism.

Hydraulic turbines of the Francis and propeller types are provided with a series of rotatable wicket gates arranged upstream or downstream of an impeller runner to control and guide water flow through the turbine and against the runner thereby spinning the runner to generate power. Each wicket gate is linked by an individual control linkage to a control ring which when turned simultaneously actuates all gates and positions them to control the power output of the turbine.

A wicket gate movement may be restricted by an obstruction, such as debris, which at times enters the turbine intake and is carried to the wicket gates. It is, therefore, the practice in order to avoid damage and possible destruction of the control linkage to provide a shear pin to release the obstructed wicket gate from the control linkage. As a gate released from its linkage is free to rotate, stops have been provided to limit such rotation thereby preventing interference and damage to the neighboring gates.

It has been found that the water force acting upon a gate free from its control linkage will cause the gate to vibrate and flutter, sometimes slamming the gates against the stops. The resulting momentum of the gate, which is a product of rotational velocity times the large mass comprising the gate, is at times'of such extreme magnitude that the stops are either bent over and wedge under the gate or broken off completely. In some cases where larger stops have been utilized, the momentum has caused the main shaft of the wicket gate to be twisted out of shape.

To overcome this potential harm to the wicket gate and the wicket gate stop, gate damping mechanisms have been provided which limit the flutter of the gate after the shear pin has been fractured. Such a device is shown in U.S. Pat. No. 3,060,706 issued to P. D. Hess, Oct. 30, I962 and assigned to the same assignee as this invention. Such devices as that disclosed in the Hess patent, although desirable in that they do in most cases prohibit damage to the gate shafis or gate stops, require that the shear pin be replaced since it has fractured. This shear pin replacement is both expensive and time consuming.

It is therefore a general object of this invention to provide a device which will indicate that the force being transmitted by the gate control mechanism is approaching a magnitude which would cause the shear pin to fracture.

An additional object is to provide a device of the hereinbefore described type wherein'a strain gauge is provided in the gate control mechanism which indicates when the magnitude of the force in the mechanism is approaching that force which will fracture the shear pin.

A more specific object of the subject invention is to provide a device of the above-described character wherein the strain gauge initiates a signal to the governor control valve which automatically stops the closing motion of the wicket gate control mechanism when a predetermined force has been exceeded.

These and other objects of the subject invention will become more fully apparent as the following description is read in light of the attached drawing wherein:

FIG. 1 shows a schematic control system which is connected to a strain gauge in the wicket gate strain pin;

FIG. 2 is a partial side elevation in section showing the wicket gate operating lever arm with a strain pin having a strain gauge therein;

FIG. 3 is a partial sectional view taken along the line Ill-Ill in FIG. 2; and

FIG. 4 is an enlarged isometric view of a suggested type of strain pin having strain gauges attached thereto.

Referring to the attached drawing wherein like reference characters indicate identical parts in the various views. a plurality of circumferentislly spaced wicket gates 6 are rotatably mounted in a stationary ring 7 about the axis of the turbine runner (not shown). Each wicket gate is provided with a shaft 8 which is connected to a hub link 9 in any conventional manner such as by the key connection 1 1 shown in FIG. 2.

As shown herein for purposes of illustration, the hub link 9 is provided with a bore 12 which is in alignment with a bore l3 provided in an operating lever 14. A strain pin 16 is provided in these aligned bores to connect the operating lever 14 and the hub link 9. In this particular embodiment the operating lever 14 extends beyond the strain pin 16 and is provided with an enlarged bore 17 which encircles a shoulder 18 provided on the hub link 9.

Each wicket gate is provided with the above described hub link and operating lever connection and also with a connecting link 19 (FIG. 1). Each connecting link is in turn pivotally connected to an operating ring 21. The operating ring 21 is rotated by one or more servomotors (not shown) which may be connected to the ring 21 by means of a lug 22 rigidly connected to the ring and pivotally connected to the servomotoroperating piston rod 23.

As best shown in FIGS. 3 and 4 and shown herein for purposes of illustration, only the strain pin 16 is provided with a pair of opposed flat surfaces 25 to which are connected conventional strain gauges 26. Means are provided in the fonn of bores 24 through the strain pin to electrically connect the strain gauges to a conventional Wheatstone bridge as shown schematically in FIG. 1.

In operation, if it is desired to slow down the turbine runner. the governor pilot servo valve is operated to activate the servomotor piston rod 23 to initiate closing of the wicket gates 6 by means of rotating the control ring 21. If an obstruction is blocking the closing of a particular wicket gate, the force in the control linkage increases. As the force in the operating mechanism increases, the resistance in the strain gauge 16 changes, disturbing the balance of the Wheatstone bridge which, as a result, emits a signal to the relay. The relay then provides an electrical current to the solenoid valve which is activated to move the governor pilot servo valve to the neutral position stopping further movement of the wicket gate control mechanism.

With this arrangement, the operator is aware that some obstruction is in the wicket gate mechanism which prohibits a normal closing of the wicket gates. This causes the gates closing operation to be interrupted before damage is done to the operating mechanism or the wicket gates. This permits the operator to inspect the wicket gates and remove any debris that has been collected between the gates and then initiate a further closing of the gates without requiring any part to be replaced.

It should be understood that the strain gauge does not have to be placed on the strain pin but may be placed at any point in the operating mechanism which is exposed to the force imposed on the wicket gates during the closing operation. If this invention is utilized on an existing machine which includes a shear pin, the strain pin could be substituted for the shear pin. When this invention is utilized on a new machine, no shear pin would be required, and the stress could be monitored from the push-pull rod connecting the gate arm to the gate operating ring.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

I. In a hydraulic turbine having a plurality of wicket gates positioned for pivotal movement between open and closed positions and actuating linkage connected to said gates for selectively positioning said gates, the improvement comprising: stress responsive means attached to said linkage adapted to indicate the stress in said actuating linkage; and means connected to said stress responsive means adapted to emit a signal when the stress in said linkage has exceeded a predetermined amount.

2. The hydraulic turbine improvement set forth in claim I wherein said stress responsive means is a strain gauge.

3. The combination with a hydraulic turbine having a plurality of wicket gates positioned for pivotal movement between open and closed positions of force transmitting means connecting said wicket gates to impart pivotal movement thereto and to prohibit relative movement therebetween, a strain gauge connected to said means and trical resistance comparing means electrically connected to said strain gauge and adapted to emit an electrical signal when the resistance in said strain gauge equals a predetermined resistance. adapted to change in electrical resistance as the force trans- 5 mitted by said force transmitting means changes and an elec- 

1. In a hydraulic turbine having a plurality of wicket gates positioned for pivotal movement between open and closed positions and actuating linkage connected to said gates for selectively positioning said gates, the improvement comprising: stress responsive means attached to said linkage adapted to indicate the stress in said actuating linkage; and means connected to said stress responsive means adapted to emit a signal when the stress in said linkage has exceeded a predetermined amount.
 2. The hydraulic turbine improvement set forth in claim 1 wherein said stress responsive means is a strain gauge.
 3. The combination with a hydraulic turbine having a plurality of wicket gates positioned for pivotal movement between open and closed positions of force transmitting means connecting said wicket gates to impart pivotal movement thereto and to prohibit relative movement therebetween, a strain gauge connected to said means and adapted to change in electrical resistance as the force transmitted by said force transmitting means changes and an electrical resistance comparing means electrically connected to said strain gauge and adapted to emit an electrical signal when the resistance in said strain gauge equals a predetermined resistance. 